Trump Jr., the eldest child of President Trump, was grilled by the House Intelligence Committee privately on Wednesday but has yet to testify in a public setting before any of the congressional committees investigating Russian meddling in the 2016 presidential election and possible collusion with the Trump campaign.

“Though he claimed to be fully cooperating with the Judiciary Committee investigation, Mr. Trump, Jr. did not initially turn over these communications.

Trump, Jr.’s “refusal” to testify before Senate Judiciary publicly means that “key questions have been left unanswered.”

Questions related to Russia and the Trump campaign “can only be answered if Mr. Trump, Jr. is compelled to fully cooperate with the committee’s investigation,” Blumenthal writes, asking Grassley issue a subpoena on behalf of the committee immediately.